Sonia Sandroni

University of Siena | UNISI · Museo Nazionale del'Antartide, Earth Science Section

Between Permian to Triassic, the Earth experienced climatic and biotic crises, included the greatest mass extinction at the Permian-Triassic boundary. These climatic and biological changes are reflected in both marine and terrestrial depositional systems. Over this time span, the Gondwana supercontinent hosted numerous large basins that may preserv...

In Antartide sono state segnalate numerose foreste fossili, molte delle quali sono datate al Permiano-Triassico. Nel corso di recenti spedizioni geologiche nell’ambito del Programma Nazionale di Ricerche in Antartide è stata rinvenuta e studiata una delle più importanti in termini di quantità e qualità dei tronchi fossili silicizzati, in posizione...

The lowest 501 m (~1139-638 m) of the AND-2A core from southern Mc- Murdo Sound is the most detailed and complete record of early Miocene sediments in Antarctica and indicates substantial variability in Antarctic ice sheet activity during early Miocene time. There are two main pulses of diamictite accumulation recorded in the core, and three signif...

The provenance of Ross Sea Drift deposits from the McMurdo Sound region (Antarctica), ranging from middle Quaternary to a Last Glacial Maximum (LGM) age, has been investigated by means of petrographic techniques. A total of 19 bulk till samples from four areas was analyzed for three different granulometric fractions: pebble to cobble, granule, and...

Central Dronning Maud Land (DML; East Antarctica) is located in a key region of the Gondwana supercontinent. The Conradgebirge area (central DML) consists of orthogneisses, derived from both volcanic and plutonic protoliths, and minor metasedimentary rocks, intruded by Cambrian syn- to post-metamorphic plutons and dykes. Mafic-ultramafic boudins in...

Permian-Triassic deposits characterize largely Allan Hills, located at the edge of the East Antarctica Ice Plateau in the northern part of the Southern Victoria Land. Here, they show an extensive exposure of some hundreds meters thick siliciclastic continental succession of the Permian to Early Jurassic Beacon Supergroup. We present preliminary dat...

Along the Transantarctic Mountains (TAM), one of the most important, thick and wide fluvial-dominated system of the southern Gondwana crops out extensively. It is represented by the Beacon Supergroup, Devonian to Early Jurassic in age, subdivided in the Taylor and Victoria groups and separated by main erosional surfaces, whereas it lies unconformab...

About 34 million years ago (Ma) Earth’s climate cooled and an ice sheet formed on Antarctica as atmospheric CO2 fell below ~750 ppm. Sedimentary cycles from a drill core in western Ross Sea provide the first direct evidence of orbitally-controlled glacial cycles between 34–31 Ma. Initially, under atmospheric CO2 levels ≥ 600 ppm, a smaller Antarcti...

Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23–14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those...

In Antarctica, northern Victoria Land is a very suitable area for the study of the Ross Orogeny, as rocks and structures of this belt are well exposed. In northern Victoria Land, the boundary between the Wilson and the Bowers Terrane is known as the Lanterman-Mariner Suture zone. Such suture is characterised by a complex structural architecture: di...

The Allan Hills are located at the edge of the East Antarctica Ice Plateau in the northern part of the Southern Victoria Land and they show an extensive exposure of several hundreds meters thick siliciclastic continental succession of the Late Permian to Early Jurassic Beacon Supergroup. We present here a preliminary report of the stratigraphic-sed...

Petrological investigations of the sand fraction and of granule- to cobble-sized clasts in the Plio-Pleistocene sedimentary cycles of the AND-1B drill core at the NW edge of the Ross Ice Shelf (McMurdo Sound) highlight significant down-core modal and compositional variations. These variations provide: (i) direct information about potential source r...

Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87 m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600 m and 40Ar/39Ar ages for in-situ volcanic deposits as well as...

Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87 m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600 m and 40Ar/39Ar ages for in-situ volcanic deposits as well as...

The Italian Museo Nazionale dell’Antartide (www.mna.it) was established as a consortium of three universities (Genova, Siena, Trieste) in 1996 with the aim to preserve, study, and increase the value of all material collected during the Italian Antarctic expeditions, as well as to promote public understanding of Antarctic science. All three sections...

Il Museo Nazionale dell’Antartide nasce nel 1996 (decreto del Ministro dell'Università e della Ricerca Scientifica e Tecnologica) ed è articolato in tre sezioni con competenze scientifiche differenziate: biologico-ecologiche (sezione di Genova), geologico terrestre e glaciologiche (sezione di Siena) e geologico marine (sezione di Trieste). Il Museo...

In northern Victoria Land (Antarctica) the Lanterman-Mariner suture separates the inboard Wilson Terrane from the outboard Bowers and Robertson Bay terranes. This boundary is characterized by the presence of discontinuous bodies of mafic to ultramafic rocks with a metamorphic grade ranging from medium-P amphibolite facies (Mountaineer Range) to ult...

About 34 million years ago, at the Eocene–Oligocene (E–O) transition, Earth's climate underwent a substantial change from relatively ice-free “green house” conditions to a glacial state marked by the establishment of a permanent ice sheet on Antarctica. Our understanding of the Antarctic cryospheric evolution across the E–O climate transition relie...

The Museo Nazionale dell’Antartide was established in 1996 and is comprehensive of three sections characterised by different scientific aims: biology and ecology (Genova section), Earth science (Siena section) and marine geology and Antarctic exploration (Trieste section). The Museum has the aim to preserve, study, and increase the value of all sci...

The Andrill AND-2A drill core documents the last 20 myr of the geological history of the Ross Sea region. In this work we date detrital apatites from the upper 1000 m by three different techniques on the same grain: U-Pb (UPb), fission-track (AFT) and U-Th/He (AHe) analysis. The UPb data clearly indicate that most of apatites derive from a crystall...

A petrological investigation of amphibole-bearing metamorphic clasts in the ANDRILL AND-2A core allows a detailed comparison with similar lithologies from potential source regions, leading to the identification of three distinct provenance areas in the present-day segment of the Transantarctic Mountains between the Byrd Glacier and the Blue Glacier...

A petrological investigation of basement clasts in the ANDRILL AND 2A core allows a detailed comparison with similar lithologies from potential source regions, leading to the identification of three distinct provenance areas in the present day segment of the Transantarctic Mountains between the Byrd Glacier and the Blue Glacier (Mulock Skelton glac...

In 2007, the Antarctic Geological Drilling Program (ANDRILL) drilled 1138.54 m of strata ∼10 km off the East Antarctic coast, including an expanded early to middle Miocene succession not previously recovered from the Antarctic continental shelf. Here, we present a facies model, distribution, and paleoclimatic interpretation for the AND-2A drill hol...

In 2007, the Antarctic Geological Drilling Program (ANDRILL) drilled 1138.54 m of strata ∼10 km off the East Antarctic coast, including an expanded early to middle Miocene succession not previously recovered from the Antarctic continental shelf. Here, we present a facies model, distribution, and paleoclimatic interpretation for the AND-2A drill hol...

This paper includes the results of a detailed quantitative provenance investigation on gravel-size clasts occurring within the late Early to Late Miocene sedimentary glacimarine section recovered for the first time by the AND-2A core in the SW sector of the Ross Sea (southern McMurdo Sound, Antarctica). This period of time is of crucial interest, a...

About 34 million years ago, at the Eocene-Oligocene (E-O) transition, Earth's climate underwent a substantial change from relatively ice-free "green house" conditions to a glacial state marked by the establishment of a permanent ice sheet on Antarctica. Our understanding of the Antarctic cryospheric evolution across the E-O climate transition relie...

Terra Nova, 22, 361–368, 2010 Detrital apatite fission-track data combined with provenance analysis of gravel-fraction detritus are used in this study to investigate the Neogene exhumation of the West Antarctic Rift System. Samples have been collected from the upper 1000 m of the ANDRILL AND-2A drill core, which documents the Miocene history of the...

ampling of interstitial fluids during deep coring in southern McMurdo Sound, Antarctica, revealed the presence of seawater-sourced, hypersaline brine at depths >200 m below the seafloor. Na-Cl-Br and SO4-Cl-Br relationships are consistent with a concentration mechanism that involves the removal of pure H2O as ice and precipitation of mirabilite (Na...

The sedimentary sequences under the McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line position, main ice-stream flows during glacial and interglacial periods. Statistical analyses on detritital clay and heavy...

The Italian Museo Nazionale dell’Antartide was established in 1996 with the aim to preserve, study, and increase the value of all the scientific materials collected during the Italian Research expeditions in Antarctica. The Earth Science section of the museum (University of Siena) holds a permanent exhibition to promote the knowledge of the Antarct...

Study of erosive products of orogenesis contributes towards understanding of timing and consequences of continental deformation. Low-temperature detrital thermochronology provides valuable information about cooling in the source terrane and offer a means of sampling over a larger area. In this work we apply detrital apatite fission-track (AFT) dati...

An integrated investigation including provenance analysis of the gravel-fraction and detrital apatite fission-track (AFT) thermochronology on the AND-2/2A core provides new results to constrain the exhumation history of source regions and the reconstruction of sediment provenance models in the in the Ross Embayement in Late Cenozoic time. Provenanc...

The cryosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences underlying the modern McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, groundin...

Significant down-core modal and compositional variations are described for granule- to cobble-sized clasts in the Early Pliocene to Middle/Late Miocene sedimentary cycles of the AND-1B drill core at the NW edge of the Ross Ice Shelf (McMurdo Sound). Long-term shifts in compositional patterns outline an evolving provenance which is interpreted as re...

Eclogite facies rocks along the Paleozoic active margin of Gondwana are rare. They are limited to isolated segments of Northern Victoria Land (Antarctica), western Tasmania, and southeastern Australia. New petrological data for mafic rocks and their host garnet-kyanite schists from the Franklin Metamorphic Complex (western Tasmania) permit reconstr...

The vertical distribution of lithofacies from glacimarine sequences recovered during the Cape Roberts Project displays cyclicity,which is interpreted as the sedimentary response to fluctuations in relative sea level. These changes are associated with climatic cycles and/or cycles of glacial advance and retreat (e.g. CRP Science Team, 2001; Naish et...

An exceptional triple palynological signal (unusually high abundance of marine, freshwater, and terrestrial palynomorphs) recovered from a core collected during the 2007 ANDRILL (Antarctic geologic drilling program) campaign in the Ross Sea, Antarctica, provides constraints for the Middle Miocene Climatic Optimum. Compared to elsewhere in the core,...

The criosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences under the McMurdo ice-shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line posit...

Magnetic susceptibilities of pebble- to cobble-sized clasts recovered in the ANDRILL SMS core (site AND-2A: 77° 45.488'S, 165° 16.605'E) (McMurdo Sound, Ross Sea) were measured on ice with a Bartington MS-2B susceptibility meter. Measurements were made on thin section billets or on clasts themselves when they were of suitable size for the instrumen...

In northern Victoria Land, at the Pacific end of the Transantarctic Mountains, a major suture zone separates the inboard Wilson Terrane, characterized by low- to high-grade metamorphism, from two low-grade outboard terranes, the Bowers and the Robertson Bay Terranes (Weaver et al., 1984). This boundary, a complex fault zone, runs more than 400 km f...

Preliminary data on clast distribution and petrology of basement clasts in the Pleistocene to Early Miocene sedimentary succession recovered by the AND-2A drill hole (southern McMurdo Sound, Antarctica) are described. Clasts ranging in size from granule- to boulder-size class were logged and counted on the basis of lithology, which mainly includes...

The ANDRILL (AND-1B) core is revealing a great potential to contribute new essential constraints on the dynamics of the West Antarctic Ice Sheet (WAIS) and Ross Ice Shelf/Sheet system, as well as to understand the behavior of the East Antarctic Ice Sheet (EAIS) outlet glaciers during the Late Cenozoic. Petrological investigations of the sand fracti...

New geological, petromagnetic and petrological information on basement rock units of the Ross Orogen in Southern Victoria Land are compiled together with literature data in a new geopetrographic map integrating and refining the published maps that covered only partially the region. In the Byrd Glacier area (Britannia Range), the map is based on the...

Petrological investigations of the sand fraction and of granule- to cobble-grade clasts and in the uppermost 586 m of the ANDRILL (AND-1B) drill-core highlight significant downcore modal and compositional variations, which provide i) direct information about the potential source regions, ii) evidence of an evolving provenance, most likely as result...

During the on-ice logging phase, 97 725 clasts ranging in size from granule- to boulder-size were counted and logged for their abundance, compositions, distribution, shape and other textural features (i.e. diagenetic effects such as rings, nodules, etc.). The observed distribution patterns highlight significant downcore modal and compositional vari...

During the 2007 - 2008 austral spring season, the ANDRILL Southern McMurdo Sound Project recovered a core 1138 metres long (AND-2A) from a location in the southern McMurdo Sound near the Dailey Islands. This core contains a range of lithologies, including various types of terrigenous clastic diamictite, conglomerate and breccia, sandstone and mudro...

The compositional record of the AND-2A drillcore is examined using petrological, sedimentological, volcanological and geochemical analysis of clasts, sediments and pore waters. Preliminary investigations of basement clasts (granitoids and metasediments) indicate both local and distal sources corresponding to variable ice-volume and ice-flow directi...

Summary. Granule- to cobble-grade clasts in the uppermost 575 m of the MIS drill-core (AND-1B) highlight significant downcore modal and compositional variations, which provide direct information about the potential source regions and evidence of an evolving provenance, most likely as results of variable ice conditions and ice-flow directions during...

The three Cape Roberts Project (CRP) drill holes represent a cumulative recovery of a c. 1.5 km thick succession, documenting the evolution of the western Victoria Land Basin (Southern Victoria Land, SVL) from latest Eocene (c. 34 Ma) through to late Early Miocene (c. 17 Ma), and in Plio-Pleistocene time. The analysis of clast distribution patterns...

From 1997 to 1999, three overlapping drill holes (the CRP holes) cumulatively recovered a 1472-m record of glacimarine succession recording the sedimentation history in the Victoria Land Basin, Western Ross Sea (Antarctica) from late Eocene to early Miocene. This work deals with the gravel-fraction analysis of the sediments recovered by these cores...

Glacimarine sequences recovered during the Cape Roberts Project display a cyclical organization reflecting changes in relative sea-level associated with climatic cycles and/or cycles of glacial advance and retreat (CRP Science team, 2000). Based on available bio- and magnetostratigraphic data (CRP Science Team, 2001; Florindo et al., 2005) the CRP-...

This paper reports and discusses the distribution, petrography and mineral chemistry of granule- to boulder-size clasts in the Early Pliocene to Quaternary sedimentary succession recovered by the CIROS-2 drill hole, located near the mouth of the Ferrar Glacier (McMurdo Sound). In the Pliocene interval (166.47–99.27 mbsf), Early Paleozoic basement g...

The site for CRP-3, 12 km east of Cape Roberts (77.006°S; 103.719°E)was selecte to overlap the lower Oligocene strata cored in nearby CRP-2/2A, and to sample the oldest strata in the Victoria Land Basin (VLB) for Paleogene climatic and tectonic history. As it transpired there was underlap of the order of 10s of metres. CRP-3 was cored from 3 to 939...

Petrographical, mineral chemistry and distribution data on pebble- to boulder-size clasts in the Early Miocene-Late Eocene sedimentary succession recovered at CIROS-1 drillsite (McMurdo Sound) are described. Clasts are dominated by granitoids and dolerites, with minor occurrences of sedimentary, volcanic and metamorphic rocks. Granitoid clasts are...

Petrographical, mineral chemistry and distribution data on pebble- to boulder-size clasts in the Early Miocene-Late Eocene sedimentary succession recovered at CIROS-1 drillsite (McMurdo Sound) are described here. Clasts are dominated by granitoids and dolerites, with minor occurrences of sedimentary, volcanic and metamorphic rocks. Granitoid clasts...

Granulite metamorphic complexes showing migmatitic structures are widespread in several areas of the East Antarctic Shield (e.g. Ravich & Kamenev, 1975). New occurrences are reported and petrologically described from four distinct high-grade terrains: 1) the Mesoproterozoic basement of central Dronning Maud Land (cDML), strongly reactivated during...

Granulite metamorphic complexes showing migmatitic structures are widespread in several areas of the East Antarctic Shield (e.g. Ravich & Kamenev, 1975). New occurrences are reported and petrologically described from four distinct high-grade terrains: 1) the Mesoproterozoic basement of central Dronning Maud Land (cDML), strongly reactivated during...

The international Cape Roberts Project drilled three holes (CRP-1, 2/2A, 3), distributed along a SE-NW trending traverse at 16-8 km from Cape Roberts in the McMurdo Sound (southern Ross Sea, Antarctica). The 3 holes comprehensively recovered an almost continuous c. 1600 m thick section of Cenozoic glacio-marine sediments at the western margin of th...

Distribution patterns and petrographical and mineral chemistry data are described for the most representative basement lithologies occurring as clasts in the c. 824 m thick Tertiary sedimentary sequence at the CRP-3 drillsite. These are granule to boulder grain size clasts of igneous and metamorphic rocks. Within the basement clast assemblage, gran...

Distribution patterns and petrographical and mineral chemistry data are described for the most representative basement lithologies occurring as clasts in the c. 824 m thick Tertiary sedimentary sequence at the CRP-3 drillsite. These are granule to boulder grain size clasts of igneous and metamorphic rocks. Within the basement clast assemblage, gran...

Distribution patterns and petrographical and mineral chemistry data are described for the most representative basement lithologies occuring as clast in the c. 824 m thick Tertiary sedimentary sequence at the CRP-3 drillsite. These are granule to bolder grain size clasts of igneous and metamorphic rocks. Within the basement clast assemblage, granito...

Distribution patterns, petrography, whole-rock and mineral chemistry, and shape and fabric data are described for the most representative basement lithologies occurring as clasts (granule to boulder grain-size class) from the 625 m deep CRP-2/2A drillcore. A major change in the distribution pattern of the clast types occurs at c. 310 mbsf, with gra...

Distribution patterns, petrography, whole-rock and mineral chemistry, and shape and fabric data are described for the most representative basement lithologies occurring as clasts (granule to boulder grain-size class) from the 625 m deep CRP-2/2A drillcore. A major change in the distribution pattern of the clast types occurs at c. 310 mbsf, with gra...

Distribution patterns, petrography, whole-rock and mineral chemistry, and shape and fabric data are described for the most representative basement lithologies occurring as clasts (granule to bolder grain-size class) from the 625 m deep CRP-2/2A drillcore. A major change in the distribution pattern of the clast types occurs at c. 310 mbsf., with gra...

Metasedimentary granulite-facies rocks from Deep Freeze Range (northern Victoria Land) are characterized by migmatitic structures and by the presence of garnet- and/or orthopyroxene-bearing leucosomes. Granulites form structural-relic bodies within a polydeformed high-grade gneissic complex. They show a multistage-metamorphic evolution, including a...

The site for CRP-3, 12 km east of Cape Roberts (77.006°S; 163.719°E), was selected to overlap the lower Oligocene strata cored in nearby CRP-2/2A, and to sample the oldest strata in the Victoria Land Basin (VLB) for Paleogene. The new data sets will drive a re-evaluation of the relationship between initiation of uplift of the Transantarctic Mountai...